Roll coating of glass fibers

ABSTRACT

A roll coater for placing binder on the fibers prior to being wound around a rotating drawing drum. The drawing drum draws fibers out of orifices in the bottom of a slowly reciprocating furnace. The fibers form a mat on the drawing drum that is later removed and expanded. The roll coater includes a graphite or other material coating drum that rotates in a bath of liquid binder and/or wetting agents, and reciprocates with the furnace. The fibers scrape over the surface of the coating drum after being formed but before winding around the drawing drum. The binder and/or wetting agent picked up on the surface of the coating drum coats the fibers with binder and/or wetting agent. Liquid binder and/or wetting agent is replenished in the bath in which the coating drum is partially submerged by a float, sensor, pump and large container of binder/wetting agent.

(e) BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to formation of a glass fibermat using the method commonly referred to as the Modigliani method, andmore particularly relates to a means and method for coating the glassfibers with binder and/or wetting agents after formation but beforecollecting in a mat.

[0003] 2. Description of the Related Art

[0004] Fiberglass mats, which subsequently can be infiltrated with amatrix material such as a polymer resin to form a composite, are formedconventionally by different methods. One method for making fiberglassmats is described in several patents to Modigliani, U.S. Pat. Nos.2,546,230; 2,609,320 and 2,964,439, all of which are herein incorporatedby reference.

[0005] These patents disclose an apparatus in which a slowlyreciprocating, melting furnace feeds molten glass through spinningorifices which discharge an array of fine, continuous glass filaments orfibers that are wrapped circumferentially around a rapidly rotatingdrawing drum. The melting furnace reciprocates relatively slowly in alongitudinal direction above the drum's rapidly rotating circumferentialsurface, thereby forming a build-up of continuous fibers oriented atacute angles with one another. During winding of the fibers on therotating drum, a binder, such as a thermosetting resin, is applied byspraying the fibers already deposited on the drum to bind the fibers attheir overlapping junctions with fibers of previously deposited layers.

[0006] After a suitable thickness of fibers has been created, thecondensed mat is removed from the drum by forming a longitudinal cutthrough the mat parallel with the axis of the drum. The condensed mat issubsequently deposited on a conveyor belt that moves at a very slowrate. The severed condensed mat is generally rectangular in shape, andthe fibers in the mat extend, due to the orientation of the rectangularmat on the conveyor, substantially completely across the width of themat substantially perpendicular to the direction of movement of theconveyor belt.

[0007] At the exit end of the conveyor belt, a retarding roller pressesthe condensed mat against the conveyor belt, which is supported by anoppositely rotating support roller. The leading end of the condensed matbeyond the retarding roller is stretched or expanded longitudinally upto hundreds of times its original, condensed length. The expanding is acontinuous process with the leading end being pulled longitudinallywhile the retarding roller/support roller structure minimizes theforward movement of the remaining length of the condensed mat.

[0008] As the mat expands longitudinally, it also expands (“fluffs”) inthe direction of the mat's thickness to a consistency resembling cottoncandy. And during the expansion of the mat, the fibers that areoriginally oriented transversely to the direction of movement are pulledlongitudinally, thereby tending to rotate and reorient the fibers to a45 degree or greater angle with respect to the longitudinal direction.During the expansion process, in which the original mat increases inlength enormously and “fluffs” to a significantly greater thickness, themat necks down to a smaller width.

[0009] After the majority of the expanding takes place, the fluffed,expanded mat is compressed in the direction of its thickness by rollingand it is heated by radiant heaters to set the thermosetting resinincorporated during the winding of the fibers on the drum. Thereafter,the stretched glass fiber mat is wound on a spool, on which it may betransported to other locations for use in various structures such asheat, thermal and sound insulation, mechanical parts formed, forexample, by pultrusion or molding, and filters.

[0010] The conventional manner of placing the binder on the fibers is tospray the layer of fibers with a binder after the fibers are woundaround the drum. However, this spray coats not only the layer of fibersjust wound, but to some extent also further coats fibers that were woundearlier, and were coated sufficiently with binder already. Additionally,when the binder is placed on the outwardly facing sides of the fibers,enough binder must be sprayed to wet the fibers so that the contactpoints between fibers (on the other sides of the fibers) contain binder.This results in superfluous coating of fibers with binder, which resultsin unnecessary expense and potentially undesirable properties due toexcessive binder.

[0011] Therefore, the need exists for a method and apparatus thatapplies binder and/or a wetting agent to the fibers only to the extentnecessary to cause the fibers to bind to one another.

(f) BRIEF SUMMARY OF THE INVENTION

[0012] The invention is an improved apparatus for forming a fiberglassmat. The apparatus includes a glass-containing furnace that reciprocatesalong a reciprocation path near a drawing drum. The drawing drum ismounted to rotate around a drawing drum axis. The drawing drum axis isaligned substantially parallel to the path of furnace reciprocation fordrawing glass fibers along a fiber path extending from furnace orificesto the drawing drum. This apparatus winds the glass fibers around thedrawing drum to form a mat.

[0013] The improvement comprises a coating drum having an axis aboutwhich the coating drum is rotatably mounted. The coating drum isdisposed with a circumferential surface in the fiber path. A prime moveris drivingly linked to the coating drum for driving the coating drumabout its axis. The coating drum preferably reciprocates with thefurnace.

[0014] In a preferred embodiment there is also a bath containing a poolof liquid binder and/or wetting agents in which at least a portion ofthe circumferential surface of the coating drum is submerged for pickingup binder and applying it to the fibers. In a still more preferredembodiment, a coating drum cleaner, such as a wide brush, is mountedwith a cleaning edge in contact with the circumferential surface of thecoating drum. The brush cleans debris from the circumferential surfaceof the coating drum.

[0015] The binder or wetting agents applied by the invention is appliedprior to the deposition of fibers onto the drawing drum but after fiberformation from the furnace. The invention eliminates the need forspraying the fibers after deposition on the drawing drum, thereby savingthe cost of superfluous binder and/or wetting agents, and makingexpansion of the condensed mat much easier.

(g) BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016]FIG. 1 is a schematic view in perspective illustrating the entirefiber mat forming machine with which the invention is operated.

[0017]FIG. 2 is a side view illustrating the preferred embodiment of thepresent invention.

[0018] In describing the preferred embodiment of the invention which isillustrated in the drawings, specific terminology will be resorted tofor the sake of clarity. However, it is not intended that the inventionbe limited to the specific term so selected and it is to be understoodthat each specific term includes all technical equivalents which operatein a similar manner to accomplish a similar purpose. For example, theword connected or term similar thereto are often used. They are notlimited to direct connection, but include connection through otherelements where such connection is recognized as being equivalent bythose skilled in the art.

(h) DETAILED DESCRIPTION OF THE INVENTION

[0019] The apparatus 2 with which the present invention is used is shownin FIG. 1. The drawing drum 4 is rotatably mounted about an axle 6 thatis rotatably driven by a conventional drive means 8, such as an electricmotor. The drive means 8 may be directly linked to the axle 6, or it maybe driven through a linkage (not shown). The axle 6 is rotatably mountedin a bearing 9, thereby permitting continuous, rapid rotation of thedrum 4 about the axle 6.

[0020] The glass-containing, reciprocating furnace 10 is disposed abovethe drawing drum 4 with the glass fibers 12 extending from the lower endthereof toward the drawing drum 4. The lower end of the furnace 10contains orifices through which molten glass contained in the furnace 10flows to form larger diameter, very slowly flowing streams. The moltenglass streams begin to cool as they pass through the orifices, and withthe lower ends wound around the rapidly rotating drawing drum 4, themolten glass streams are drawn into the much smaller diameter continuousfibers 12 as they move at a speed on the order of 1,900 feet per minutenear the drawing drum's surface. The fibers 12 extend along a fiber paththat begins at the furnace 10 and ends where the fibers contact thecircumference of the drawing drum 4.

[0021] The fibers 12 are spaced apart in an array that is commonlyapproximately two inches thick by about 12 inches wide. Of course, theseare only representative dimensions that can be varied greatly to suit aparticular set of circumstances as will be understood by a person havingordinary skill in the art. This array is ordinarily angled relative tothe axis of the drawing drum 4 from as much as 90 degrees to as littleas 45 degrees, and preferably about 75 degrees. This angle causes a 12inch wide and two inch thick array of fibers to form a layer of fiberson the circumferential surface of the drawing drum 4 less than 12 inchesonce the spaces between the fibers in the array are reduced toessentially zero. For example, for the array discussed above at a 75degree angle, the width of the layer might be approximately four inchesin a conventional machine. With the preferred embodiment of the presentinvention, the width can be reduced to approximately one inch or evenless.

[0022] The reduction in the width of the layers of fibers is due to theroll-coater 20 in FIG. 1. The roll coater 20 is interposed along thelength of the fiber path between the furnace 10 and the point of contactof the fibers 12 with the drawing drum 4. The roll-coater 20 will bedescribed in more detail presently with reference to FIG. 2.

[0023] The roll coater 20, which is mounted between the furnace 10 andthe drawing drum 4, is most preferably drivingly linked to the furnace10 by the link 11, and is preferably disposed beneath the furnace 10 andabove at least the part of the circumferential surface of the drawingdrum 4 where the fibers 12 first contact the drawing drum 4. The rollcoater 20 includes a bath 22 that contains a pool of liquid binder 24having an upper surface 26. The term “binder/wetting” agent refers toconventional agents used to bind glass fibers together. This term alsoincludes wetting agents in combination with the glass fiber binder or asan alternative to a conventional glass fiber binder. The coating drum 30is rotatably mounted about its axle 32 to a member rigidly mounted tothe bath 22 with the lower part of the circumferential surface of thecoating drum 30 submerged beneath the surface 26 of the binder/wettingagent 24 (as shown in hidden lines in FIG. 2). The coating drum 30 ispreferably about three inches in diameter and its outer surface isgraphite due to the low friction properties and lack of reaction ofgraphite with glass and conventional binders/wetting agents. Of course,the coating drum 30 could be made of a material other than graphite,such as a ceramic, polished bronze or a low friction polymer sold underthe trademark DELRIN, depending upon compatibility with thebinder/wetting agent and glass.

[0024] One side of the endless loop drive chain 34 extends around asprocket (not shown) on the axle 32 of the coating drum 30. The oppositeside of the drive chain 34 extends around a different sprocket 36drivingly linked to the driveshaft 38 of a prime mover, such as theelectric motor 40. This drive means is merely exemplary, of course, andit will be understood by the person having ordinary skill thatequivalent drive means could be substituted therefore, including a beltor rope drive, direct shaft drive, hydraulic or pneumatic drive, linearmotor, etc. Furthermore, the preferred prime mover could be replaced bya different prime mover, such as a hydraulic or pneumatic motor, aninternal or external combustion engine or some other prime mover.

[0025] The coating drum 30 is driven to rotate about the axle 32 at aspeed on the order of 40 to 100 revolutions per minute (rpm) in thedirection shown by the arrow 35, and the outer, circumferential surface33 revolves around the axle 32. The surface 33 is partially submerged inthe binder/wetting agent 24 while its distal side contacts the fibers12. This apparatus carries the binder/wetting agent from the bath 22 tothe fibers 12 in a layer on the circumferential surface 33 that has athickness determined by the surface tension and viscosity of the liquidand the molecular attraction between the liquid and the coating drum 30.

[0026] When the fibers 12 contact the layer of binder/wetting agent onthe circumferential surface 33, the fibers become coated withbinder/wetting agent and carry that binder/wetting agent to the drawingdrum 4 shown in FIG. 1. The binder/wetting agent adheres to the pointsof contact between the already-deposited fibers and the fibers that arebeing deposited. Once cured, the binder/wetting agent functions in theconventional manner to bind the fibers together to form the mat.

[0027] The fibers 12 that contact the drum surface 33 have the spacesbetween them reduced to at least some extent, thereby “compressing” thearray from its original size, for example 12 inches by two inches, to anew size, for example less than 12 inches wide and the thickness of afew fibers. Therefore, when the new, compressed array is wound aroundthe drum 30, its width is on the order of an inch.

[0028] The new, compressed array mat that is formed is thinner, forexample 30% to 35% thinner than conventional mats of the same weight perunit area, but with more individual tows of fibers rather than beingfilamentized as with the prior art mats. This results in a final matthat is more of an open weave, which provides better wet-throughproperties with resin that is later applied to the mat to form thecomposite's matrix.

[0029] Additionally, because the invention only coats each fiber withbinder/wetting agent once, as opposed to the prior art in which thefibers are coated many times by spraying and overspray, the mat expandsmuch more easily. Therefore, the cost of the excess binder/wetting agentis saved and the ease in expanding the mat is enhanced with the presentinvention.

[0030] As binder/wetting agent is removed from the bath 22 and placed onthe fibers, the upper surface 26 begins to drop. The float 50, whichfloats in the binder/wetting agent 24 and is mounted to the sensor 52,drops with the upper surface 26 of the binder/wetting agent 24. When thefloat 50 drops to a predetermined position, the sensor signals a smallpump (not shown) through the wires 56 to pump more binder/wetting agentfrom a larger container into the bath 22 through the tube 54, which hasa passageway in fluid communication with the interior of the bath 22.Once the float 50 raises with the upper surface 26 to a secondpredetermined position, the sensor 52 signals the pump to stop pumpingmore binder/wetting agent into the bath 22.

[0031] A cleaner, preferably a scraping blade or the brush 60, ismounted with its inner edge contacting the circumferential surface 33 ofthe coating drum 30. The brush 60 contacts the coating drum 30 andextends the entire width of the circumferential surface 33 to scrapeagainst the circumferential surface 33 and stop any fibers or fiberpieces that may break off of the array extending from the furnace 10.The brush 60 also evens out the layer of binder/wetting agent on thecircumferential surface 33 so that it is even when the fibers contactit.

[0032] It can be seen from the above description that as the coatingdrum 30 rotates at a speed much slower than the fibers 12 passing overthe outer surface of the coating drum 30, the fibers will pick upbinder/wetting agent that will cause the deposited fibers to bindtogether. The binder/wetting agent preferably wets the entire outersurface of the fibers 12. There is a reduced need for spraying binder,with its attendant waste of binder due to spraying fibers multipletimes, and there is only as much binder in the finished product as isnecessary to ensure binding at most or all intersections of fibers.Therefore, one embodiment includes spraying in addition to applying witha coating drum and another only applies binder with a coating drum.Finally, this invention places binder/wetting agent on the entire outersurface of each fiber prior to depositing it on the already-depositedfibers, which ensures that binder/wetting agent is positioned on theparts of the fibers that will seat against already-deposited fibers. Theprior method of spraying the fibers after deposition does not ensuresuch placement of the binder.

[0033] While certain preferred embodiments of the present invention havebeen disclosed in detail, it is to be understood that variousmodifications may be adopted without departing from the spirit of theinvention or scope of the following claims.

1 through
 9. (Cancelled)
 10. A method of applying binder/wetting agentto a plurality of fibers that are formed by drawing the fibers through afiber path extending downwardly from orifices in a glass-containingfurnace that reciprocates along a reciprocation path above a drawingdrum to the drawing drum, said drawing drum being rotated around an axisthat is aligned substantially parallel to the path of furnacereciprocation, and winding the glass fibers around the drawing drum, themethod comprising: (a) drivingly linking a roll coater to the furnace,the roll coater including a coating drum, having an axis about which thecoating drum is rotatable mounted, below the furnace orifices and abovethe drawing drum with a circumferential, side surface of the coatingdrum in the fiber path, and in contact with substantially all of thefibers extending downwardly from the furnace orifices to the drawingdrum, the roll coater also including a bath below the furnace orificesand the coating drum, the bath containing a pool of liquidbinder/wetting agent in which at least a portion to the circumferentialsurface of the coating drum is submerged for picking up binder/wettingagent and applying it to substantially all of the fibers; and (b)rotating the coating drum about its axis.
 11. (Cancelled)
 12. The methodin accordance with claim 10, further comprising scraping thecircumferential surface of the coating drum for removing debris from thecircumferential surface of the coating drum.
 13. The method inaccordance with claim 12, further comprising reciprocating the coatingdrum and bath with the furnace.
 14. A method of applying binder/wettingagent to a plurality of fibers that are formed by drawing the fibersthrough a fiber path extending downwardly from orifices of aglass-containing furnace that reciprocates along a reciprocation pathabove a drawing drum to the drawing drum, said drawing drum beingrotated around an axis that is aligned substantially parallel to thepath of furnace reciprocation, and winding the glass fibers around thedrawing drum, the method comprising: (a) drivingly linking a roll coaterto the furnace, the roll coater including a coating drum, having an axisabout which the coating drum is rotatable mounted, below the furnaceorifices and above the drawing drum with a circumferential, side surfaceof the coating drum in the fiber path, and in contact with substantiallyall of the fibers extending downwardly from the furnace orifices to thedrawing drum, the roll coater also including a bath below the furnaceorifices and the coating drum, the bath containing a pool of liquidbinder/wetting agent in which at least a portion to the circumferentialsurface of the coating drum is submerged for picking up binder/wettingagent and applying it to substantially all of the fibers; (b) rotatingthe coating drum about its axis; (c) scraping the circumferentialsurface of the coating drum for removing debris from the circumferentialsurface of the coating drum; and (d) reciprocating the coating drum andbath with the furnace.